The present invention relates to a semiconductor device disposed in a small area.
A module unit of semiconductor devices is used in order to densely dispose semiconductor devices and in order to obtain a small-sized electronic apparatus. Such semiconductor devices (module unit) comprise a plurality of semiconductor integrated circuit chips and other electronic parts, such as condensers, mounted on a ceramic base plate which comprises multilayer printed wiring patterns. The ceramic base plate is mounted on a printed board so that it forms various electronic circuits.
A leadless package (a leadless chip carrier) has been developed in order to dispose semiconductor packages in a small area. The leadless package comprises electrode films formed on the surface instead of lead terminals projecting from the side surface of the package. A plurality of leadless packages are mounted on a ceramic base plate which is mounted on a printed board, so that each leadless package is connected to a circuit pattern formed on the printed board. These leadless packages are used especially when there is a strong demand for dense mounting of semiconductor packages. Therefore, the surface of the ceramic base plate must be effectively used for mounting the leadless packages and also the surface of the printed board must be effectively used for mounting the ceramic base plate.
In the semiconductor devices comprising leadless packages according to the prior art, the leadless packages are mounted by soldering only on one main surface of the ceramic base plate. Therefore, semiconductor devices of the prior art do not effectively use the area of the ceramic base plate surface and the printed board surface.